This application makes reference to, incorporates the same herein, and claims all benefits accuring under 35 U.S.C. xc2xa7119 from my application MICROWAVE OVEN filed with the Korean Industrial Property Office on Oct. 11, 2000 and there duly assigned Serial No. 59845/2000.
1. Field of the Invention
The present invention relates in general to microwave ovens, and more particularly, to a microwave oven having an improved grill cover.
2. Description of Related Art
Referring to FIG. 6 which is an exploded perspective view of a conventional wall-mounted microwave oven, the conventional microwave oven is comprised of a main body 101 formed with a cooking compartment 103, and an outer casing 105 surrounding the main body 101, to define an outer appearance of the microwave oven.
A tray 107 upon which food rests is placed within the cooking compartment 103. In front of the cooking compartment 103 is installed a door 109 opening and closing the cooking compartment 103, through which a user can put in and pick out the food. Beside the door 109 is installed a control panel 111 formed with a plurality of buttons by which the user can control the microwave oven. In the rear of the control panel 111 is installed a magnetron 115 supplying electromagnetic waves into the cooking compartment 103.
The outer casing 105 is comprised of an upper casing 117, a lower casing 121 and a rear casing 119. The upper casing 117 takes a shape of inverse xe2x80x98U,xe2x80x99 surrounding the upper part and both side parts of the main body 101, the lower casing 121 is installed in the lower of the main body 101 and the rear casing 119 is installed in the rear of the main body 101.
On the lower casing 121 are installed a pair of air inlet ports 127 and a pair of hood lamps 129. Through the air inlet ports 127, air flows into the lower casing 121, according to operation of a blowing fan 125 installed to the rear casing 119, and the hood lamps 129 is installed adjacent to the air inlet ports 127, to illuminate below the microwave oven.
On the top face of the upper casing 117 is formed an exhaust port 123 through which the air drawn through the air inlet ports 127 is exhausted outside the main body 101. Between the upper of the main body 101 and the upper casing 117 is formed a grill member 135 having a number of air passing holes 133. On the top of the main body 101 is formed a holding bracket 131 holding the grill member 135. In front of the grill member 135 is provided a grill cover casing 141, taking a shape of rectangular box, having longitudinal openings in the front face and the rear face thereof. In the front opening of the grill cover casing 141 is installed a grill cover 143. Between the grill member 135 and the grill cover 143 is provided a switch 161 opening and closing the grill cover 143 installed in the front opening of the grill cover casing 141.
FIG. 7 is a partial, sectional view showing an assembly of the grill cover 143 and the switch 161 taken along line VIIxe2x80x94VII of FIG. 6, and FIG. 8 is a view showing an operation state of the grill cover of FIG. 6. As shown therein, the grill cover casing 141 is comprised of an inclination part 142 downwardly inclined toward the inside of the front opening thereof, with a predetermined inclination degree. On the outer upper surface of the grill cover casing 141 is formed an indentation part 141a indented from the surface thereof to a predetermine depth. On the outer lower plate of the grill cover casing 141 is formed a protrusion part 141b protruded transversely relative to the lower plate thereof. The grill cover casing 141 is allowed to closely contact an upper portion of the main body 101 and a lower surface of the upper casing 117 by means of the indentation part 141a and the protrusion part 141b. On the grill cover 143 installed in the front opening of the grill cover casing 141 is formed a link supporter 147 protruded toward the grill member 135 transversely, relative to the grill cover 143.
The link supporter 147 has an elongated guide hole 147a (see FIG. 8) formed in the lengthwise direction thereof. On opposite sides of the rear lower portion of the grill cover 143 is provided a hinge 149 coupled to the grill cover casing 141, opening and closing the front opening of the grill cover casing 141. In the middle of the grill cover casing 141 is formed a bracket 165 taking a shape of inverse xe2x80x98U.xe2x80x99 One side of the bracket 165 is opened and the other side thereof is coupled to the grill member 135. The switch 161 opening and closing the grill cover has a step motor 163 having a rotational shaft to drive of opening and closing of the grill cover 143, and a link shaft 167 coupled to the rotational shaft of the step motor 163. The step motor 163 is coupled to an external side of the bracket 165. On one end of the link shaft 167 is formed a motor shaft accommodating part 167a coupled to the rotational shaft of the step motor 163. On the other end of the link shaft 167 is formed a connection pin 167b connected to the elongated guide hole 147a of the link supporter 147.
The connection pin 167b is accommodated in the elongated guide hole 147a, so as to slidably elevate along the elongated guide hole 147a. When the grill cover 143 is closed, the connection pin 167b is placed in the upper side of the elongated guide hole 147a of the link supporter 147.
Referring to FIG. 8 again, in the case that the grill cover 143 is opened, if the step motor 163 is activated for a predetermined period of time according to a signal from a controller (not shown), so that, for example, the motor shaft is rotated counterclockwise in view of the motor 163, the link shaft 167 coupled to the rotational shaft of the step motor 163 is rotated counterclockwise. If the link shaft 167 is rotated counterclockwise, the connection pin 167b of the link shaft 167 is slid downward along the elongated guide hole 147a. If the connection pin 167b is slid downward, the grill cover 143 is forward rotated, to thereby open the front opening of the grill cover casing 141. After a predetermined period of time has passed, the controller (not shown) activates the step motor 143 to stop its operation. If the step motor 163 stops, the grill cover 143 remains in the maximally opened state. At this time, the step motor shaft connected to the link shaft 167 supports the weight of the grill cover 143.
In the case that the opened grill cover 143 is closed, if the rotational shaft of the step motor 163 is rotated clockwise by a control signal from the controller (not shown), the link shaft 167 coupled to the rotational shaft of the step motor 163 is rotated clockwise. If the link shaft 167 is rotated clockwise, the connection pin 167b of the link shaft 167 is slid upward along the elongated guide hole 147a of the link supporter 147. If the connection pin 167b is slid upward, the grill cover 143 is rotated backward, to thereby close the front opening of the grill cover casing 141. After a predetermined period of time has passed, the controller (not shown) activates the step motor 163 to stop its operation. If the step motor 163 stops, the grill cover 143 is closed. That is, the step motor 163 draws the grill cover 143 connected to the link shaft 167 by the rotation of the rotational shaft of the step motor 163.
In the conventional microwave oven, while the operation to open the grill cover is being conducted, the weight of the grill cover is to be supported by the rotational shaft of the motor, thereby generating an excessive burden to the rotational shaft. Further, while the operation to close the grill cover is being conducted, the grill cover is to be drawn by the rotation force of the motor, thereby generating an over-load to the motor.
To open and close the grill cover, the motor has to be rotated reciprocally rather than unidirectionally, and frequent reciprocation of the motor is likely to cause the motor to be out of order. To open and close the grill cover, the connection pin connected to the link shaft should be slid up and down along the elongated guide hole of the link supporter, thereby preventing smooth open and close operations. In addition, since the grill cover is opened and closed by operating the motor for a predetermined period of time, it is not easy to maintain open and close range. Also, the conventional microwave oven requires a step motor that is more expensive than other motors, thereby increasing the cost of production.
Accordingly, the present invention has been made in view of the above-described shortcomings, and it is an object of the present invention to provide a microwave oven capable of smoothly opening and closing the grill cover, maintaining the open and close range, and reducing the cost of production.
This and other objects of the present invention may be achieved by a provision of a microwave oven comprising a main body formed with a cooking compartment, an outer casing surrounding the main body, to define an outer appearance of the microwave oven, a grill member provided between the main body and the outer casing, having a number of air passing holes, and a grill cover rotatably provided in front of the grill member, opening and closing the grill member, further comprising a main cam rotatably contacting with a rear face portion of the grill cover; a motor moving the main cam; and a switch sensing a rotational position of the main cam, the rotational position of the main cam being controlled to control the opening/closing operation of the grill cover when the motor operates.
The switch comprises a first micro switch operated to suspend the rotation of the main cam and the operation of the motor when the main cam is rotated to a predetermined degree to correspond to an open position of the grill cover; and a second micro switch operated to suspend the operation of the motor when the main cam is rotated to a predetermined degree from the open position, to correspond to a closed position of the grill cover.
The microwave oven further comprises first and second auxiliary cams to respectively activate the first and second micro switches when the main cam is rotated to correspond to the open and closed positions of the grill cover.
The main cam, the first auxiliary cam and the second auxiliary cam are provided coaxially. The microwave oven further comprises a spring provided at the rear of the grill cover, elastically biasing the grill cover from the open position to the closed position.
A reinforced steel plate is provided on the rear face of the grill cover, to prevent the grill cover from being deformed.